"It does not matter if my warranty is expired. Chevy designed the power assist and should replaced any defective parts on it or make these parts avaliable to the public, instead of charging $800.00 to fix a desigin flaw that they caused."
Yes, it does matter if your warranty is expired. The purpose of the warranty is to cover the cost of repairing/replacing defects. It has a specific time and mileage limit. They may have extended coverage for certain VINs, but they did this as a goodwill gesture. Bottom line, they are not required to do anything for you after the warranty period expires. The exception would be a safety related recall ordered by NHTSA. Since that hasn't happened, you don't have a leg to stand on.
I'm not saying that this is a good thing. I've owned several vehicles that displayed obvious design defects after the warranty period had expired. All car makers have them. It's not fun, but that's the way it is. With the exeption of the recall process, manufacturers are only required to cover defects during the warranty period.